1. Field of the Invention
The present invention relates generally to an ultrasonic detection sensor and more particularly to an ultrasonic transducer formed of alternating layers of piezo ceramic and plastic mounted on a thick film substrate.
2. Description of the Prior Art
It is known to use ultrasonic signals to detect distances between bodies. Generally, an ultrasonic transducer is mounted on one body to emit an ultrasonic signal which is reflected by a second body disposed at a distance from the first, after which the transit time of the reflected signal from the second body is evaluated. The emitting transducer and the receiving transducer can also be mounted separately from one another at respective first and second bodies disposed opposite one another; this, however, requires two separate transducers. Beside the bodies on which the transducers are mounted, there can also be other boundary surfaces reflecting the ultrasonic signal such as, for example, the surface of a liquid. This concept is used in liquid level detectors using ultrasonic signals, whereby an ultrasonic transmission is reflected back into the liquid at a surface or reflected back to the outside of the liquid from the surface. It is known, for example, to provide tank measuring apparatus, in particular for fuel tanks in motor vehicles. One of such tank measuring apparatus includes an ultrasonic transducer mounted at the bottom of a fuel tank to emit an ultrasonic signal that is reflected at the surface of the fuel situated in the tank and returned to a transducer (which may also be the transmitting transducer). Electronic circuitry for evaluating a signal from such tank measuring apparatus is also known as is shown in the laid open German Pat. No. OS 30 03 317.
When ultrasonic transducers are to be used in large numbers as, for example, in motor vehicles it is necessary to have transducers which are both effective as well as of simple and rugged construction. It is also desirable to provide transducers which are relatively inexpensive to manufacture.